JPH01206A - powder manufacturing equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a powder manufacturing apparatus for manufacturing metal powder used in powder metallurgy and the like.

[Conventional technology]

Powder metallurgy is a technology for manufacturing metal products or metal ingots by charging metal or alloy powder into a mold, press-molding it, and then sintering the molded body. In powder metallurgy, segregation of component elements does not occur, it is possible to commercialize materials that are difficult to process, it is possible to obtain parts with extremely fine crystal structures, and it is possible to make non-equilibrium phases appear. There are various advantages that cannot be obtained with melted lumber, such as:
There is also the advantage that secondary cutting can be omitted. For this reason, various powder manufacturing techniques applied to powder metallurgy have been developed.

Among these, representative devices for producing powders such as high alloys and Ti alloys include rapid solidification method using centrifugal force, rotating electrode method,
There are powder manufacturing devices using centrifugal granulation methods, etc. FIG. 4 is a schematic diagram showing an apparatus for rapid solidification. In this device, by applying a high frequency current to a high frequency coil 22, a metal lump is melted in a container 21, and the generated molten metal 23 is caused to fall onto a disk 24 rotating at high speed.
The rotation of causes the molten metal 23 to scatter. Then, this scattered molten metal 23 is rapidly solidified using a cooling medium with high thermal conductivity such as hydrogen gas or helium gas.

FIG. 5 is a schematic diagram showing an apparatus for the rotating electrode method.

In this device, an arc 33 is generated between a consumable electrode 31 and a non-consumable electrode 32, and at this time, the consumable electrode 31 is rotated at high speed by a rotating means (not shown) such as a motor.
Powder 35 is obtained by scattering droplets 34 generated by melting of consumable electrode 31 .

FIG. 6 is a schematic diagram showing an apparatus for centrifugal granulation.

In this device, a crucible 41 is rotatably installed in an argon gas atmosphere, and an electrode 42 is installed vertically.
Droplets 44 are formed by generating an arc 43 between the electrodes 42 and rotating the crucible 41 while cooling it with water to melt the electrodes 42.
By dropping the liquid into the crucible 41, the droplets 44 are scattered and powder is generated.

However, all of these devices have problems that must be solved. In rapid solidification equipment, molten metal 23
It is difficult to produce high-purity powders of Ti, Ti alloys, high alloys, superalloys, etc. due to the risk of impurities getting mixed in from the container 21 that stores the 0-rotation electrode method and centrifugal granulation method. In this case, there is a risk that impurities may be mixed in from the non-consumable electrode 32 and the crucible 41, although the amount is smaller than in the rapid solidification method. Additionally, devices using these three methods have a problem in that the manufacturing speed is slow. Furthermore, in the case of devices using these three methods, it is necessary to water-cool the non-consumable electrode 32 and the rotating crucible 41, which consumes 50% of the power consumption.
is taken away by this water-cooled electrode, resulting in low powder production efficiency (,
This is extremely disadvantageous in terms of energy economy. Furthermore, in these devices, the consumable electrode 21 made of the alloy to be obtained is
, and the crucible 41 that acts as a water-cooled electrode needs to be rotated at high speed in order to obtain powder with small particle size.
In order to rotate these electrodes at high speed, there are additional difficulties in terms of the processing accuracy of the electrodes and the rotation mechanism.

Furthermore, in the rotating electrode method, in order to rotate the electrode at high speed, the diameter of the electrode needs to be as small as about 60+ m at maximum, and there is also the problem that the electrode manufacturing cost is high.

[Problem that the invention seeks to solve]

The present inventors conducted research to solve these various problems, and the results were previously published in Japanese Patent Application No. 61-221343.
No. (filed date: September 19, 1986).

The seventh tooth is a schematic diagram of a powder manufacturing apparatus according to an embodiment of Japanese Patent Application No. 61-221343. In this device, an arc 52 is generated between electrodes 51 to melt the tips of the electrodes 51 and generate droplets 53 of molten metal that fall onto a disk 54 . The disk 54 is rotating at high speed, and the droplets are scattered by centrifugal force and cooled to become powder 55. Both of the electrodes 51 are consumable electrodes, and have a structure that does not rotate at high speed.

As mentioned above, in Japanese Patent Application No. 61-221343, consumable electrodes are used for both electrodes, so there is no risk of contamination with impurities (there is no need to water-cool the electrodes, and production can be increased). Also, since the electrodes are not rotated at high speed, the mechanism of the device is simplified.Also, the diameter of the electrodes is, for example, 20 mm.
Since the diameter can be as large as 0 Tsuru, the electrode manufacturing cost can be reduced and the processing capacity can be increased. Therefore, the powder cost is also reduced.

In this way, Japanese Patent Application No. 61-221343 is an excellent method that solves the problems of the prior art, but still,
There were the following problems.

When an arc is generated between the electrodes to melt the tips of the electrodes and droplets of molten metal are scattered by a disk rotating at high speed,
The droplets must fall onto the disk so that they fall almost straight down, but in order to make the droplets fall almost straight down, it is necessary to keep the arc generation in a stable state. In order to stabilize the generation of arc, it is necessary to reduce the pressure inside the chamber. The degree of pressure reduction is preferably a high vacuum, and the upper limit of the allowable pressure is around 5 QTorr. When the pressure exceeds approximately 59 Torr, arcing occurs only in a part of the electrode, or no arcing occurs, making it extremely unstable. In such cases, the direction of droplet fall also changes. It often happens that it is disturbed and does not fall onto the disk.

On the other hand, when the droplets that have fallen onto the disk are scattered and cooled in an atmospheric gas such as argon gas or helium gas,
Since it is necessary to rapidly cool the powder and the solidification must be completed before the droplets collide with the inner wall of the chamber, the cooling efficiency must be increased.

In order to increase the cooling efficiency, it is required to make the pressure of the atmospheric gas as high as possible, and in order to rapidly cool the droplets and achieve the above purpose, the pressure of the atmospheric gas, which is the cooling medium, must be 50 Torr or more. , preferably at 100 Torr or higher.

Furthermore, since the pouring speed and dropping position of the droplets dripping from the tip of the electrode are unstable and inconsistent, the scattering state of the droplets from the disk is unstable. The parts may spring up or fly off before reaching the edge of the disc. As a result, there is a problem that powder having a particle size larger than the desired particle size is obtained.

In this way, in Japanese Patent Application No. 61-221343, in order to simultaneously satisfy the conditions for stabilizing the arc and the conditions for rapidly cooling the droplets, the pressure must be kept almost constant around 5QTorr, and the conditions must be adjusted. There was the above difficulty.

The present invention, together with the problems of conventional powder manufacturing equipment,
This was done to solve the problems of No.-221343, and it is possible to produce powders of Ti+Ti alloys, high alloys, superalloys, etc. with high purity, efficiently, and at low cost, and the mechanism of the device is simple. It is an object of the present invention to provide a powder manufacturing apparatus which can have a small chamber, can obtain quenched powder, and can stably manufacture desired powder.

[Means for solving problems]

The present invention includes a plurality of electrodes installed at intervals in a chamber, a droplet forming means for generating an arc between these electrodes to form droplets of molten metal, and an annular side wall on the outer periphery of the upper surface. The chamber is provided with a disk disposed at a position where the droplets fall, and a disk rotation means for rotating the disk to scatter and cool the droplets into powder, and an arc is provided in the chamber. A partition wall is installed to separate the space in which droplets are formed from the space in which the droplets are scattered and cooled by the rotation of the disk, and this partition wall has a communication portion that allows the droplets to pass through and has ventilation resistance. This is the powder manufacturing equipment installed.

[For production]

In the present invention, a partition wall is installed in the chamber to divide the space into a space where droplets are formed and a space where the droplets are scattered and cooled, so that the pressure in the rain space is controlled within the target range. Can be set.

For example, the space where droplets are formed by an arc is set to 10 Torr.
The space in which the s droplets are scattered can be set to 100↑orr. Therefore, quenched powder can be obtained while maintaining arc stability. In the space where droplets are formed,
An arc is created between multiple electrodes to form droplets of molten metal that fall onto a rapidly rotating disk. Due to the centrifugal force caused by the rotation of the disk, these droplets become finer droplets and are scattered from the upper end of the side wall of the disk. The scattered droplets are rapidly cooled in a space where the droplets are scattered and cooled, and instantly become powder.

〔Example〕

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

The chamber 61 is divided by a partition wall 62, with an upper part serving as a droplet formation space 63 and a lower part serving as a droplet cooling space 64. The droplet formation space 63 is provided with an exhaust hole 65 connected to an exhaust means (not shown) such as a vacuum pump, so that it can be maintained at a highly reduced pressure. The droplet cooling space 64 is provided with an inlet 66 for introducing an atmospheric gas such as argon gas or helium gas, and is made to have a higher pressure than the droplet forming space 63, so that a pressure difference can be created between the two spaces. In the droplet formation space 63, a plurality of electrodes 67 having, for example, the same composition as the powder to be manufactured are installed at appropriate length intervals with a portion of the electrodes in the elongated direction. A current is supplied to this electrode 67 from an electric aI 68 to generate an arc 69 between the electrodes 67, melting the opposing ends of the electrode 67, and producing droplets 70 of molten metal. The liquid droplet 7 is placed on the partition wall 62.
A communication portion 71 is provided directly below where the droplets 70 fall, forming a passage through which the droplets 70 fall into the droplet cooling space 64. The communication portion 71 is designed to have a small opening area within a range that allows droplets to pass through, and to have a large ventilation resistance. A disk 73 that rotates at high speed by means of a disk 72 is installed, and has a structure in which falling droplets 70 are scattered.

Note that the drive device 74 for the electrodes 67 is configured to drive the electrodes 67 facing each other.
It is equipped with a feeding mechanism to maintain a constant spacing between the two. It also has a function of gently rotating the electrodes 67 in the same direction or opposite directions, so that the electrodes 67 can be melted uniformly and the arc 69 can be generated in a favorable state.

Further, a plurality of atmospheric gas introduction holes 66 are provided to prevent uneven flow of the atmospheric gas in the droplet cooling space 64.

Further, as a means for maintaining the degree of reduced pressure in the droplet formation space 63,
In addition to exhausting air from the exhaust hole 65 , exhaust is also performed from the droplet cooling space 64 to reduce the amount of atmospheric gas flowing into the droplet formation space 63 through the communication part 71 , and the exhaust gas connected to the exhaust hole 65 is also exhausted. It is also possible to reduce the load on the means.

In the powder manufacturing apparatus configured in this way, the power source 6
8 supplies power to the electrode 67 to generate an arc 69, melting the opposite ends of the electrode 67 and producing droplets 70 of molten metal. During this time, the electrodes 67 are moved little by little by the drive device 74 so that the spacing between the electrodes 67 is always constant. At this time, the pressure in the droplet formation space 63 is 50To
Since the air is exhausted from the exhaust hole 65 to maintain the temperature below rr, preferably below 1QTorr, the arc between the electric bridges 67 is stabilized, and the droplets fall almost directly below. The fallen droplet 70 enters the droplet cooling space 64 through a communication portion 71 provided in the partition wall 64 and falls onto a disk 73 rotating at high speed. Due to centrifugal force, the droplets 70 that have fallen onto the disk hit an annular side wall 73 protruding from the outer periphery of the upper surface of the disk, and are scattered from the upper end into finer droplets, which are then dispersed into atmospheric gases such as argon gas and helium gas. It is instantaneously cooled and becomes powder 75. In this case, the atmospheric gas is introduced so that the pressure in the droplet cooling space 64 is 50 Torr or more, preferably 100 Torr or more, thereby increasing the concentration of the atmospheric gas and improving the cooling efficiency.
Solidification is completed before colliding with the inner wall of 1, and it becomes a quenched powder.

As mentioned above, since it is possible to create a pressure difference between the droplet forming space 63 and the droplet cooling space 64, even if there are pressure fluctuations in each of the spaces, the pressure in each space remains within the limit. This is acceptable, and the conditions for stabilizing the arc 69 between the electrodes 67 and the conditions for rapidly cooling the droplet can be easily adjusted.

FIG. 2 is a schematic diagram showing another embodiment. In this embodiment, the structure of the partition wall that divides the chamber 61 into a droplet forming space 63 and a droplet cooling space 64 is changed. A rotating disk 73 is provided. The partition wall consists of a plane partition wall 62a that vertically divides the droplet formation space 63 and the droplet cooling space 64, and upright partition walls 62b and 62C installed around the cylindrical sedisc 73. There is. The partition walls 62b and 62c have the same shape, and the disk 7
3. It is installed close to above and below the extension plane of the upper end. A gap between the partition walls 62b and 62c is formed in the communication portion 71 and is provided over the entire circumference.

In this device, droplets 70 generated by melting the electrode 67 fall onto the disk 73 and are scattered, pass through the communication section 71 and enter the droplet cooling space 64 . The droplets entering the droplet cooling space 64 are cooled by the atmospheric gas and solidify into powder before colliding with the inner wall of the chamber 61.

In this embodiment, the path for the droplet 70 to fall from the electrode 67 to the disk 73 can be widened, so even if the falling direction of the droplet 70 changes slightly, the droplet 70 can adhere to the partition wall. The advantage is that there is no problem.

Note that, as described above, since a pressure difference is maintained between the droplet forming space 63 and the droplet cooling space 64, the partition walls 62b and 6
2c should be as close to the disk 74 as possible, have a size that allows the droplets to scatter due to centrifugal force at a high speed, and be installed in a position where the droplets do not spread, so that the droplets can pass through even the narrow communication portion 71. Furthermore, in order to further facilitate the maintenance of the pressure difference, a partition wall is provided which is a combination of the partition wall 62 in FIG. 1 and the partition walls 62b and 62c in FIG.
It is preferable to provide communication portions at two locations: the path through which the 0 particles fall from the electrode 67 and the path through which the droplets scatter from the disk, to increase ventilation resistance.

In the present invention, a side wall is provided protruding from the upper surface of the disk.
This is due to the following reason. The droplet formed at the tip of the electrode does not fall at a constant speed, and the droplet position is also not constant. For this reason, if a disk with a smooth top surface is used, the scattering state will become unstable, and phenomena such as some of the droplets jumping up at the droplet position or scattering before reaching the periphery of the disk may occur. There is a problem in that a powder that is larger than the powder to be obtained is obtained. In the present invention, by providing a protruding side wall, droplets are reliably scattered from the periphery of the disk, thereby stabilizing the scattering state and making it possible to obtain powder with a desired particle size. The inner diameter of the side wall of the disk is 2
For the purpose of obtaining powder of 00 μm or less, 150 μm of the disk
When rotating from 0Orpm to 30000rpm, 50~
200n is suitable. Further, if the height of the side wall is too low, the centrifugal force will not work sufficiently, and if it is too high, it will be difficult to rotate the disk at high speed, so it is preferable that the height of the side wall is about 100 to 100 W. As for the shape of the side wall, various shapes shown in cross section in FIG. 3(a) to r+ can be used. Note that FIG. 3A is a plan view of the disk shown in FIG. 3Fa.

Disk materials include graphite, boron nitride, zirconium boride (ZrBz), water-cooled copper,
Examples include stainless steel.

Note that when manufacturing titanium or titanium alloy powder, it is preferable to construct the disk from the same material as the powder to be obtained in order to prevent contamination from the disk.

Next, a specific example in which actual powder was manufactured according to Examples will be described. The electrode used was a Ti alloy with a composition of 16% and 4%, and a diameter of 100 mm. The device is the first
According to the configuration shown in the figure, the communicating portion 71 of the partition wall 62 has a diameter of 40*m, the disk 73 has a diameter of 9011 m, and a rotation speed of 30 m.
It was set as 0OOrp+++. When producing the powder, the droplet forming space 63 was evacuated in advance by a diffusion pump at 30,000 A/sec, and helium gas at 4 Nl/sec was introduced into the droplet cooling space 64. At the time when gas introduction and exhaust reached equilibrium, the pressure in each space was 7 Torr in the droplet formation space 63 and 9QTorr in the droplet cooling space 64. While adjusting the conditions in this way, the 672 electrodes were made to face each other, and 3,0
An arc was generated by supplying a current of 0.00 A. Electrode 6
All of the droplets 70 in which 7 was melted fell onto the disk 73 and were scattered as minute droplets. The scattered droplets did not adhere to the inner wall of the chamber, and the particle size of the obtained powder 75 was about 100 μm. Note that the dissolution rate of the electrode 67 in this case was 4.2 kg/min.

〔Effect of the invention〕

According to the present invention, since a container for molten metal, a crucible, a non-consumable electrode, etc. are not used, there is no risk of contamination with impurities, and highly pure powder can be obtained. In addition, all of the multiple electrodes use consumable electrodes, so high production rates can be maintained.
Moreover, since there is no need to water-cool the electrodes, energy efficiency is good, and since electrodes with large diameters can be used, electrode manufacturing costs are low, and powder manufacturing costs can be reduced. Furthermore, since there is no need to rotate the electrodes at high speed, the mechanism of the device can be simplified.

Furthermore, since it has become easy to simultaneously satisfy both the conditions for stabilizing the arc between the electrodes and the conditions for rapidly cooling the droplets, the molten metal droplets can fall almost directly below, and the rotation of all the disks can be controlled. In addition, the scattered droplets can be efficiently and instantaneously turned into powder.
The chamber can be made smaller. Furthermore, since the droplets can be rapidly cooled, a rapidly cooled powder in a non-equilibrium phase having a fine crystal structure can be obtained. Furthermore, since an annular side wall is protruded from the top surface of the disk, even if there are variations in the speed and position of droplets falling on the disk, the droplets can be reliably scattered to obtain powder with the desired particle size. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention. FIG. 2 is a schematic diagram showing another embodiment. 3(a) to 3(f) are cross-sectional views of the disk according to the present invention, FIG. 3(g) is a plan view of the fourth (al) disk, and FIGS. FIG. 7 is a schematic diagram showing an embodiment of the invention previously proposed by the present inventor. 61...Chamber, 62...Partition wall, 62a...
Partition wall, 62b...Partition wall, 62c...Partition wall, 6
3... Droplet formation space, 64... Droplet cooling space, 67
...electrode, d9...arc, 70...droplet, 71
. . . Communication portion, 73 . . . Disc, 75 . . . Powder. Applicant's agent Patent attorney Takehiko Suzue 1 Figure 2 Ran 3! il Figure 4 5wI

Claims (1)

[Claims] The chamber includes a plurality of electrodes installed at intervals, a droplet forming means for generating an arc between these electrodes to form droplets of molten metal, and an annular side wall protruding from the outer periphery of the top surface. , comprising a disk disposed at a position where the droplet falls, and a disk rotation means for rotating the disk to scatter and cool the droplet to form a powder, and forming the droplet in the chamber by an arc. A partition wall is installed to separate the space from a space in which the droplets are scattered and cooled by rotation of the disk, and this partition wall is provided with a communication portion that allows the droplets to pass through and has ventilation resistance. powder manufacturing equipment.